Traditionally data switches, such as Ethernet switches, which transmit data packets between input ports and output ports via a switching fabric have been operated as a component of a large computer apparatus having a reliable electrical power supply and a cooling system. More recently, however, applications for data switches have arisen in which it would be advantageous for the power requirement of the switch to be reduced. An example of such a system is an IP phone, in which data packets passing through the switch are data packets of a telephone conversation. The data switch for such devices is frequently provided within an apparatus which is hand-held or which is located in a furnished room. Excessive heat generation might make such a device uncomfortable to hold, or damage furniture which is located close to the apparatus. The excess heat might also damage the casing of the device. Furthermore, many telephones of conventional telephone systems draw their power from the telephone lines themselves, but this is only possible if the telephone requires only a low amperage. Thus, a data switch which requires a power supply greater than this level will only be useable as part of an IP telephone which has access to a separate power source.